Radiator leak
 

I used a leak detection dye and finally determined I have a leak near the top of the radiator, passenger side, and facing towards the engine. My car is a Mini S, 2003 with about 125k. I just went through major expense and hassle replacing the water pump and all the hoses (when in reality my problem was most likely the radiator all along), so before I go through the expense of a new radiator, I was wondering if this was a common problem? Note also, that I see no outward signs of corrosion or cracking, though this might not be apparent until I pull out the whole radiator and examine it closely. Currently I'm losing about a liter of coolant every 100 miles. Any thoughts or suggestions?

The inlet (top passenger side) and outlet (bottom driver side) flanges are removable and have rubber o-ring seals that tend to spring leaks. BMW/Mini does not have a part number for these and they will just tell you to buy a new rad. OEM replacements are available for not too much money ($120-$150) but no the easiest to install.

You can remove the neck via 2 nuts, fairly easily without pulling anything apart. I was unable to find a replacement o-ring so just used some liquid gasket sealant along with the original o-ring and that seems to be working so far. Hope that helps.